1. Field of the Invention
The present invention relates to a method of adjusting optical imaging system which forms an image of an object. The present invention also relates to a positional deviation detecting mark for use in detecting positional deviation of a pattern in a production process of semiconductor devices and liquid crystal display devices and a method of detecting positional deviation. The present invention further relates to a method and a device for detecting a position of a pattern on a substrate. The present invention further relates to a mark identifying device.
2. Description of Related Art
(First Related Art)
In production processes of semiconductor devices and liquid crystal display devices, a circuit pattern is transferred to a resist layer through a well known lithographic process. The circuit pattern is transferred to a predetermined material film (a pattern forming process) through processing such as etching via the resist pattern. By repeating the pattern forming process many times, circuit patterns of various material films are laminated on a substrate (a semiconductor wafer or a liquid crystal substrate) to form a circuit of a semiconductor device or a liquid crystal display device.
Further, in the production process, in order to superpose circuit patterns of various material films with high accuracy (for the purpose of improving the yield of products), the substrate is aligned before a lithographic process, and superposition of the resist patterns on the substrate is inspected after the lithographic process and prior to a machining process in the respective pattern forming processes. An alignment mark formed on an underlying layer in a preceding pattern forming process is used fro the alignment of the substrate. The superposition mark formed on the resist layer in a current pattern forming process and that formed on the underlying layer in the preceding process are used for the superposition inspection of the resist patterns.
In addition, a substrate alignment device or a device for superposition inspection of resist patterns on the substrate incorporates a device for detecting the position of the aforementioned alignment mark and superposition mark (all of which are simply referred to as the mark). The position detecting device detects the position of the mark by irradiating a mark to be detected with illumination light, capturing an image according to light from the mark (for example, reflected light) with an image pickup device such as a CCD camera, and performing predetermined image processing on the image. In order to obtain a stable reflection intensity for a wide variety of structures of the mark, the wavelength band of the illumination light is often determined to be a broad band range from a visible light band to a nearly infrared light band.
Further, in order to enhance the detection accuracy, a position detecting device finely adjusts the arrangement of an aperture stop of an optical imaging system (an optical system for forming an image of the mark) and an objective lens in the shift direction, to thereby reduce an error component induced by a device (TIS value: Tool Induced Shift), by a method, for example, disclosed in Japanese Unexamined Patent Application Publication No. 2000-77295.
(Second Related Art)
Superposition inspection (positional deviation detection) usually uses an underlying mark indicating the reference position of an underlying pattern and a resist mark indicating the reference position of a resist pattern. Each of the underlying mark and the resist mark is formed at the same time when the underlying pattern or the resist pattern are formed in the aforementioned pattern forming process, which constitutes a duplex mark 80 in a square shape as shown in FIG. 19 (for example, see Japanese Unexamined Patent Application Publication No. 7-151514). FIG. 19 is a plan view of the duplex mark 80. Generally, in the duplex mark 80, the outer mark is an underlying mark 81 and the inner mark is a resist mark 82. The size D1 of the underlying mark 81 is, for example, about 30 μm, and the size D2 of the resist mark 82 is about 15 μm. The underlying mark 81 and the resist mark 82 are arranged so that their respective centers coincide when there is no positional deviation between the underlying pattern and the resist pattern.
Then, upon superposition inspection using the underlying mark 81 and resist mark 82, a measurement point including two marks (81, 82) are positioned in the visual field of the device, capturing the image of the measurement point with an image pickup device such as a CCD camera. Further, the images of edge portions of corners of the underlying mark 81 and the resist mark 82 is clipped from the captured image, and obtained partial images are subjected to a predetermined image processing, to calculate positional deviation amount between the center of the underlying mark 81 and the center of the resist mark 82. The calculated positional deviation amount represents a positional deviation of the resist pattern relative to the underlying pattern.
(Third Relate Art)
The substrate alignment device or the device for the superposition inspection of a resist pattern on a substrate incorporates a device that detects the position of the aforementioned alignment mark and superposition mark (all of which are simply referred to as the mark). The position detecting device generally detects the position of the mark by illuminating a substrate with white light, capturing an image of the mark with an image pickup device such as a CCD camera, and performing predetermined image processing on the image (for example, see Japanese Unexamined Patent Application Publication No. 7-151514).
(Fourth Related Art)
In order to identify a mark to be measured from marks (such as the alignment mark and superposition mark) on a substrate such as a wafer with a semiconductor measuring appratus, first, a mark as a reference for identification is photographed in advance and the image thereof is registered in a recipe. Subsequently, the mark is identified by comparing a mark to be measured with the mark registered in the recipe. (for example, see Japanese Unexamined Patent Application Publication No. 9-89528).
However, according to the aforementioned method of adjusting the optical imaging system of the first related art, it is not possible to reduce the error component (TIS value) of the device sufficiently when the imaging position of the pupil image on the aperture stop surface of the optical imaging system changes depending on the wavelength band due to production error (eccentric error of optical elements) or the like in disposing respective optical elements of the optical imaging system.
In view of solving the above problem, the inventors of the present invention proposed (in Japanese Patent Application No. 2003-54058) to correct the deviation of the imaging positional of the pupil image on the aperture stop surface depending on the wavelength band by arranging a new optical element for adjustment between the pupil plane and the aperture stop surface of the optical imaging system and finely adjusting the arrangement of the optical element, using the method disclosed in Japanese Unexamined Patent Application Publication No. 2000-77295. However, it is difficult to decrease adjustment error by the method disclosed therein since the arrangement of the optical element cannot be finely adjusted with a good sensitivity. Therefore, it is not possible to reduce the error component due to the device (TIS value) sufficiently and improve the detection accuracy sufficiently.